This invention relates to improvements in self-sealing gaskets, particularly valve-like gaskets through which tubes may be inserted and removed, and in which the valve-gasket maintains a seal at all times. Devices of this type are used in a variety of environments, such as medical environments, in which it is often required to insert one tube through another tube or into a housing or vessel while maintaining the outer tube, housing or vessel sealed at all times. Other environments in which such devices have been used include gas masks or sealed helmets, to provide a self-sealing valve through which a feeding tube or the like may be inserted and withdrawn repeatedly, while maintaining a seal at all times. For example, U.S. Pat. No. 2,023,267 to DeSaint Rapt illustrates a gas mask having a self-sealing valve formed of a plurality of apertured and slitted disks arranged face-to-face through which a feeding tube may be inserted or withdrawn. Similarly, U.S. Pat. No. 3,067,425 to Colley illustrates a modified form of self-sealing device in an aviator's helmet having a different configuration of slits and apertures in the various face-to-face disks.
U.S. Pat. No. 4,000,739 to Stevens illustrates an analogous use for such a self-sealing gasket arrangement in a catheter introducer. The catheter introducer illustrated in the Stevens patent includes a tube which is intended to be inserted into and which remains in place in a patient's blood vessel. A fitting on the externally projecting end of the tube is provided with a self-sealing gasketing device to enable catheters to be introduced into the patient's blood vessel through the self-sealing introducer. The catheter introducer may remain in place in the patient's blood vessel for a period of time during which the various catheters may be inserted and withdrawn as may be determined by the particular medical procedure(s) at hand. Also illustrative of the medical environments where self-sealing valves or plugs may be used are shown in Ring U.S. Pat. No. 3,459,183 and Scislowicz U.S. Pat. No. 3,097,646 which show needles or other similar tubular introducer devices are placed in a blood vessel and in which the devices are provided with self-sealing plugs or the like on their outer ends to provide self-sealing access to the blood vessel.
When such a self-sealing device is used in a catheter introducer, it often may be desirable to provide a side entry port through which liquids may be introduced or through which the device may be aspirated (i.e. to withdraw blood or otherwise apply suction as desired). Thus, it is important that the self-sealing valve or plug maintain its seal over a relatively wide range of pressures to include not only the normal positive pressure of the patient's blood pressure but also the reduced pressure which results from aspiration through the side port. Also among the desirable features of a self-sealing device is that the seal should not unduly inhibit axial and rotary movement of a catheter through the seal.
The type of self-sealing device as illustrated in the Stevens, DeSaint Rapt and Colley patents is not without its difficulties. That type of device utilizes a number of slitted and apertured gasket disks in face-to-face relation. In each of these, it is necessary to manufacture a number of separate disks and to assemble them in a predetermined sequence and array, all of which adds to manufacturing costs. In addition, when used as a self-sealing cannula (as in the Stevens device) it has been found that while such multiple gasket devices are not wholly without difficulties. For example, the commercially available version of the device disclosed in the Stevens patent may not perform as well during aspiration as might be desired and in some instances, there is some risk that aspiration may ingest air into the system through the disks. It is believed that this is in part due to the use of two thin face-to-face gaskets which typify the Stevens construction.
It is among the general objects of the invention to provide an improved self-sealing gasket configuration for use in catheter introducers and the like.